Hydrophobic Coating Compositions and Articles Coated With Said Compositions

Abstract

Hydrophobic coating compositions are provided as are processes to coat articles with the compositions. Extremely hydrophobic coatings are provided by the compositions. Durable, weatherable and scratch-resistant coatings are provided by compositions comprising a trifluoromethyl-containing component and a hardenable material. Weatherable coatings are also provided by compositions comprising a mobile non-volatile fluorinated component and a hardenable material. Processes are also provided for forming hydrophobic coatings on articles.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]The present application is a continuation of U.S. patent application Ser. No. 10 / 898,773, filed Jul. 26, 2004, which is co-pending with this filing; which in turn is a continuation of U.S. patent application Ser. No. 10 / 272,982, filed Oct. 17, 2002, now U.S. Pat. No. 6,767,587 B1, issued Jul. 27, 2004; which in turn is a divisional of U.S. patent application Ser. No. 09 / 823,853, filed Mar. 30, 2001, now U.S. Pat. No. 6,495,624, issued Dec. 17, 2002; which in turn is a continuation-in-part of U.S. patent application Ser. No. 09 / 593,847, filed Jun. 14, 2000, now U.S. Pat. No. 6,447,919, issued Sep. 10, 2002; which in turn is a divisional of prior application Ser. No. 09 / 220,884, filed Dec. 28, 1998, now U.S. Pat. No. 6,156,389, issued Dec. 5, 2000; which in turn is a continuation-in-part of prior application Ser. No. 08 / 795,316, filed Feb. 3, 1997, now U.S. Pat. No. 5,853,894, issued Dec. 29, 1998, all of which are incorporated herein in th...

AI Technical Summary

Benefits of technology

[0033]A surprising discovery about the economics and commercial success of coating low cost, especially one-time-use, articles with fluoropolymer coatings is that process efficiency in recovering carrier solvents can be a more important factor than the relatively high cost of the coating fluoropolymers. While high quality unsaturated fluoromonomers currently can cost $250 (US) to over $1000 (US) per pound in bulk quantities, articles such as pipette tips may only require 10 to 20 milligrams of fluoropolymer per thousand pipette tips at a current cost of less than 10 cents per thousand. Conventional coating / washing equipment, for example, equipment from Renzacci of America Inc., Absecond, N.J., and from Fluoromatic Ltd., Villa Park, Ill., and processes that are designed to recover solvents, can consume over 25 grams of solvent per thousand pipette tips at a current cost of about five cents per gram or $1.25 (US) per thousand. In many situations, particularly coating methods using expensive perfluoropolymers, this is an unacceptable added cost to articles otherwise costing only a few dollars per thousand to manufacture. According to the present invention, solvent loss is significantly reduced compared to the conventional machines and processes.

[0038]According to the present invention, the coating composition comprises a trifluoromethylated agent comprised of a fluorocarbon, hydrofluorocarbon, epoxy, urethane, silicone, acrylic or other material that has a terminal trifluoromethyl group and contains from about 3 to about 20 carbon atoms. Preferably, coatings made from such compositions exhibit tightly packed trifluoromethyl groups on the exposed coating surface. According to some embodiments of the invention, coating polymers made from substantially non-branched fluorinated monomers having carbon chains of from about 3 to about 20 carbon atoms in length, and more particularly from about 6 to about 12 carbon atoms in length, enable a dense packing of the terminal trifluoromethyl groups and thus can form hydrophobic surfaces of very low surface energy, having critical surface tensions of about 10 dynes / cm or lower at 20° C., and having high resistance to solvent removal and low retention of biological samples.

Problems solved by technology

When samples are quantitatively analyzed, it can be of critical importance that precise and representative amounts of sample are transferred, or else inaccurate results are obtained.

Due to the different affinities of some materials to adhere to the walls of a laboratory vessel, qualitative analyses such as concentrations of materials may also be adversely affected if certain materials in a sample selectively adhere to operational surfaces of the vessel walls.

Unfortunately, materials typically used in the manufacture of laboratory vessels do not sufficiently repel many biological sample fluids nor do they sufficiently resist the adherence of molecular constituents of such a sample fluid.

The sample fluids often wet the surface of the vessel causing residual quantities of liquid sample to cling to an operational surface of the vessel when the sample is removed.

In some cases, significant quantitative and / or qualitative errors result.

Drawbacks associated with silane treatments include a continued wetting of the vessel, adherence to the vessel walls by many samples, chemical reactivity with many reagents, and a tendency for the vessel to become wettable following the common practice of autoclaving for sterilisation.

Silicones are known to freely migrate, leading to worries over sample integrity.

Many pipette tips are plugged with porous filters to prevent sample contamination from the pipettor barrel, yet these free silicones make the pipette tips slippery and cause the filters to become loose or dislodged.

Additionally, silicones must typically be added at a level of 2 percent by weight to be effective, making the cost prohibitive for many price sensitive applications.

This method is impractical, however, for treating the vast quantities of small vessels consumed by industrial, clinical and research establishments.

Furthermore, improvements in performance over silicone processes are only marginal.

While these methods offer improvements over silicon-based treatments, the time, expense and equipment required are not appropriate for high commercial volume articles that are often for one-time use and require very low inherent cost.

Extruded and fused Teflon® vessels are currently manufactured for special applications involving exceptionally harsh reagents but are expected to have a long service life because of their high material cost when compared to the cost of glass or polypropylene vessels.

While no attempts are known to coat laboratory vessels by such a procedure, it is expected that difficulties would arise as well as high cost in coating such vessels because of the shear bulk of the polymerizable solution to be irradiated and problems with fully washing the coated vessel.

Methods of making disposable, one-time use laboratory vessels such as pipette tips can involve a substantial loss of costly solvent when a coating solution is used to form a hydrophobic coating.

The mere suggestion of such a recovery practice, however, does not provide a commercially viable method for coating many low cost, one-time-use articles, such as pipette tips and laboratory vessels.

Operation of these machines according to their suggested protocols using fluorinated solvents, however, still results in large, expensive losses.

This translates to solvent consumption costs of over one dollar per thousand tips.

Higher boiling point fluorocarbon solvents have lower loss rates, but the solvent expense is about the same due to their higher cost per pound.

Unfortunately, at 30° C. the solvent FC84 has a vapor pressure of over one fifth atmosphere, and the half cubic meter tank volume contains about two pounds of solvent as dense vapor (about 14 times that of air), even without agitation.

Opening the tank door results in the immediate loss of this material, at a current cost of about $45 (US).

The carbon recovery filter is at the top of the tank and is of little practical economic value.

Additional losses accrue during the heat cycle at 50° C. when the machine fittings and seals are challenged by pressures approaching 1.2 atmospheres.

Furthermore, it is apparent from other studies that low molecular weight fluorocarbon solvents, having boiling points between 80° and 120° C. are particularly “slippery” in passing through rubber and silicone gaskets and seals.

No machines investigated had more aggressive containment systems for leak-free operation under these conditions.

Higher microwave frequencies have resulted in greater communication bandwidth, but the shorter wavelengths are even more susceptible to rain attenuation.

Airports report losses of vital satellite links during heavy precipitation, and most home viewers of satellite TV are familiar with programming disruption during even light rain.

As bandwidths expand commercial and private use of microwave links, the problem of rain attenuation will become even more critical.

As these coatings degrade over time due to sunlight and pollution, they become less hydrophobic and their effectiveness is diminished.

These composite coatings have good performance initially but begin to form water films in an hour or less of moderate to heavy rain.

After months or just weeks of exposure to mid-latitude summer sunlight these types of coatings wet out even more quickly.

Drying fully after being swamped, the Boyd Teflon™ dispersion coating CRC6040 recovers most of its previous performance, but the hydrophobic performance of the Vellox LC-410 fumed silicate coating is permanently lost.

It is believed that sunlight damages at least the surfaces of all solid polymers to some degree.

This need is especially acute but difficult to achieve for one-time-use vessels costing only a few dollars per thousand.